AM FM ~1955 (published: 1936) Analogue broadcasting. The World of Broadcast Radio. Armstrong & FM

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1 A Tour of Some Wireless and Mobile Communication Systems BROADCAST RADIO-Part 1 Linda Doyle Centre for Telecommunications Value-Chain Research Department of Electronic & Electrical Engineering Trinity College, University of Dublin, Ireland Analogue broadcasting The World of Broadcast Radio AM 1906 FM ~1955 (published: 1936) AM and FM are traditional technologies with which we are familiar. Radio networks are star shaped Typically there is a powerful radio transmitter covering a given area. Outside of coverage area no reception Radio receivers tend to be very cheap Fixed, portable and mobile receivers The transmissions are in one direction Armstrong & FM Armstrong first got FM working in He showed it to Radio Corporation of America, who had most of his licenses, but they were unimpressed. RCA had at that point made vast investments in AM. All of their transmitters and all of the millions of radios that they had sold used it. Radios were now commodities, and sold entirely based on price, not quality. RCA told itself that consumers didn't care what the music sounded like from their radios, they just wanted to get it as cheaply as possible. They spent a couple of years evaluating the technique and then declined to license it.

2 Armstrong Invented FM Radio When he sought permission in 1935, however, to erect an experimental FM station to demonstrate the unusual qualities of his new radio system, he ran into a stone wall. The Federal Communications Commission (FCC) dismissed FM out of hand as "a visionary development," and denied him a permit. The standard radio networks operating on AM or amplitude modulation were equally indifferent. "Who needs a second method of broadcasting?" they said. It took Armstrong nearly five years to get his experimental station constructed, after threatening to take his invention to a foreign country. FM ended up being given spectrum by the FCC in the MHz band. example of politics at play In 1945 RCA and a block of other radio companies convinced the FCC to move the FM band from MHz to MHz, where it is today. The nominal reason was to prevent "ionospheric disturbance", but no one was quite clear on what this was. The TV channel right above 50 MHz with its FM sound channel didn't seem to suffer from it. What it did do, though, was to immediately obsolete all the transmitters and receivers that had been built. To add insult to injury, the FCC also voted to severely limit FM's broadcasting power, and disallow radio relays from central stations to mountaintop antennas. Instead, the FM broadcasters had to send their material over AT&T's coax cables at exorbitant rates. The overall, and intended, result was to cripple FM broadcasting.

3 Extremely low frequency ELF 3 30 Hz Directly audible when converted to sound, communication with submarines Super low frequency SLF Hz Directly audible when converted to sound, AC power grids (50 60 Hz) Ultra low frequency ULF Hz Directly audible when converted to sound, communication with mines Very low frequency VLF 3 30 khz Directly audible when converted to sound (below ca. 20 khz; or ultrasound otherwise) Low frequency LF khz AM broadcasting, navigational beacons Medium frequency MF khz Navigational beacons, AM broadcasting, maritime and aviation communication High frequency HF 3 30 MHz Shortwave, amateur radio, citizens' band radio Very high frequency VHF MHz FM broadcasting, amateur radio, broadcast television, aviation, Ultra high frequency UHF MHz Broadcast television, amateur radio, mobile telephones, cordless telephones, wireless networking, remote keyless entry for automobiles, microwave ovens Super high frequency SHF 3 30 GHz Wireless networking, satellite links, microwave links, satellite television, door openers Extremely high frequency EHF GHz Microwave data links, radio astronomy, remote sensing, advanced weapons systems, advanced security scanning Long wave, Medium wave and Short wave can be used at times to refer to LF,MF and HF bands. Human rights group broadcast 'pirate' radio show in Beijing Updated Fri Aug 8, :32pm AEST A human rights group has broken China's tight control of the media by broadcasting a radio show calling for freedom of expression in Beijing. At 8.08am local time, the Paris based group Reporters Without Borders began a twenty minute pirate broadcast on Beijing's airwaves. Using FM transmitters they broadcast a twenty minute show on FM radio denouncing China's censorship and control of the media and free expression. It's unknown how many people were able to listen to the program. The press freedom group says it was the first radio station not controlled by the government to broadcast in China since the Communist Party took power in Wireless, not just broadcast radio can of course play this kind of role in general DAB The latest trend in the world of radio broadcasting has been a move away from analogue to digital radio We talk about DAB now digital audio broadcast The acronym DAB (Digital Audio Broadcasting) is synonymous with the Eureka 147 standard. DAB here is our first mention of a standard

4 What is DAB? compression - MPEG DAB is a digital radio broadcasting system that through the application of multiplexing and compression combines multiple audio streams (and non-audio) together for transmission. Uses MPEG audio coding for compression Uses orthogonal frequency division multiplexing (OFDM) which is robust in a multipath environment for transmission. [note: It was the first standard to include OFDM, which since then has become one of the most popular transmission schemes for modern wideband digital communication systems] When OFDM is used in conjunction with channel coding techniques, it is described as Coded Orthogonal Frequency Division Modulation (COFDM). This is what happens in a DAB system. This combination of the compression, coding and OFDM is what really defines DAB. MPEG -Moving Picture Experts Group The term refers to the family of digital video compression standards and file formats developed by the group. There are also MPEG standards for audio compression MPEG-1 Audio Layer II is actually the standard of interest for DAB DAB uses the MPEG Audio Layer II system to achieve a compression ratio of 7:1 without perceptible loss of quality. This system is modelled on the working of the human ear, and retains only the audible components of the sound. For the system to be viable the data rate has to be considerably reduced from that of a standard CD. The digital radio system adopted reduces the data rate down to kbits / sec, a sixth of the bit rate for a similar quality linearly encoded signal. To achieve these reductions the incoming audio signal is carefully analysed. It is found that the ear has a certain threshold of hearing. Below this the signals are not heard. Additionally if a strong sound is present on one frequency then weaker sounds close to it may not be heard because the threshold of hearing is modified. By analysing the incoming audio and only encoding those constituents that the ear will hear the significant reductions can be made. multiplexing More than one programme of the radio station can be transmitted at the one time from a given transmitter Note if you listen to RTE 1 on FM they sometimes split into two simultaneous programmes but to get the parallel programme you have to tune to a different frequency (e.g. Religious Services) In DAB you use multiplexing to combine the different audio services DATA can be multiplexed as well multiplexing allows for data as well typical configuration DAB can carry text and images as well as sound, and all receivers will be equipped to handle non-audio data. All but the smallest will be able to display at least two 16- character lines of text, allowing programme selection by name or programme type, and enabling broadcasters to transmit programme-associated data such as album title, song lyrics, or contact details. Additional services, such as traffic information and sports, weather or stock market news feeds, are possible. Transmission of full colour images possible. DAB Multiplex 'Bouquet' DAB stereo audio at kbps up to 9 services per multiplex

5 COFDM for dealing with multipath reminder - OFDM some details The bandwidth of the signal is 1.5MHz Much wider than the narrowband AM and FM signals The number of subcarriers in the OFDM signal is over 1500 The multiplexed audio and data streams will each have been error coded to give the robust performance required. Last Slide Explained frequencies set aside for DAB FIC: Fast Information Channel, which carries control and service information. MSC: Main Service Channel, which carries the audio and data services. Multiplexer: A device which combines all audio and data services for modulation and transmission. OFDM: Orthogonal Frequency Division Multiplexing, the modulation technique which helps avoid multi-path fading in mobile communications. Packet Mux: Combines several 'service components' (stock-market updates, weather forecasts, paging messages, etc.) into a single data service for transmission. Packet Demux: Deconstructs the single service data into separate services upon reception. Band III: DAB frequency band MHz L-Band: DAB frequency band MHz

6 A network of DAB transmitters So? DAB gives substantially higher spectral efficiency, measured in programmes per MHz and per transmitter site, than analogue communication. Apart from the multiplexing we spoke about earlier where multiple stations can be transmitted by the one transmitter, the various transmitters can all operate on the same frequency SINGLE FREQUENCY NETWORK (SFN) 1. Improved end-user features (can contain non audio information) 2. Reception quality 3. More stations (because it is more spectrally efficient) 4. Variable bandwidth 5. Less pirate interference SFN transmission can be considered as a severe form of multipath propagation. But? 1. Implementation choices leading to Sound quality issues 2. Currently limited coverage 3. Expense of the receivers 4. Expense of the system as more transmitters required (though overall have read comments on electricity savings) 5. More power needed for the receiver (hence batteries do not last as long) 6. Compatibility we have not looked at new DAB standards, DAB + the scene is not so settled The Story with RTE RTÉ has indicated to the Department of Communications that it will have a DAB network covering the South East corridor, making DAB accessible to 52% of the population, by the end of The terrestrial DAB frequencies set aside for Ireland seem to be at and MHz.

7 DAB Trial, Block 12c Transmission sites: Three Rock 10kW ERP Clermont Carn 5kW ERP Spur Hill - 5kW ERP Woodcock Hill - 5kW ERP Coverage is predicted for 1.5m above ground. Reciption threshold is: 48 dbuv/m outdoor car radio 57 dbuv/m indoor kitchen radio 64 dbuv/m pocket radio Mixed signals on digital radio Saturday, March 22nd, 2008 JOHN COLLINS IRISH TIMES 21/03/2008 RTÉ WILL cease broadcasting on medium wave (MW) next Monday just as it expands its digital radio service to cover almost half the population. This week the State broadcaster extended its trial of digital radio technology to Cork and Limerick, making it available to 44 per cent of the population. Based on the Digital Audio Broadcasting (DAB) standard, the trial broadcasts include seven new RTÉ digital radio services including a children s radio service and a dedicated news headline channel, as well as content from commercial broadcasters. However, some industry observers have wondered if the State broadcaster is backing the right technology, particularly in light of its statutory obligation to broadcast to the Irish abroad. Brian Greene, a digital media consultant, says killing MW to fund DAB is a crazy move by RTÉ because DAB has a short range while MW can be picked up by listeners in the UK. page 1 For its part, RTÉ maintains that its services are available on the Sky Digital platform and over the web. According to JP Coakley, RTÉ Radio s head of operations, the broadcaster will save 1.5 million in annual running costs by shutting down MW, of which 1 million relates to electricity costs. Coakley says the MW infrastructure had an immediate need to inject circa 2.4 million in capital as the installation is reaching the end of its natural life. The savings will not just fund DAB but a number of online projects, improvements to FM broadcasting and additional programming resources, according to Coakley. That said, national DAB has to stand as a separate business and rationale - it s about an industry moving together to provide the next generation of radio to the listener, rather than just what RTÉ can fund on its own, says Coakley. The replacement that RTÉ is proposing for MW is long wave (LW). RTÉ installed a new LW transmitter in 2007, which also supports broadcasting in a newer digital technology called Digital Radio Mondiale (DRM). page 2

8 However, Greene maintains that because DRM is more efficient, it has to be broadcast at a lower power. As a result, an Algerian radio station also broadcasting on LW252 is causing interference with RTÉ s signal. Coakley concedes Tipaza in Algeria interferes with LW252 at night in London and parts of southeast England, but points out that MW is not available at all in London. This month Greene wrote to Cathal Goan, director-general of RTÉ, raising questions about the broadcaster s transmission planning and move to digital. He also questions just how successful DAB has been in the UK, despite the fact that well over five million receivers have been sold there and the format dominates sales of kitchen, portable and clock radio sales. some DAB recordings This person has a blog that comments on RTE and its DAB system page 3 but - sound quality??? The reason why they're using insufficient bit rate levels is due to DAB using the inefficient MP2 audio codec, which needs to be used at bit rate levels of at least 192 kbps to provide good audio quality -- FM provides an audio quality which is equivalent to kbps MP2. Unfortunately, 98% of all of the stereo stations on DAB in the UK are using a bit rate level of kbps, hence the audio quality is poor. From The Guardian:- Is DAB radio the next Betamax? John Plunkett guardian.co.uk, Tuesday January SOURCE: aside Sony's Betamax video standard was introduced in 1975, followed a year later by JVC's VHS. For around a decade the two standards battled for dominance, with VHS eventually emerging as the winner. max-vhs.html OR ent.comment Digital audio broadcasting (DAB) may end up to radio what Betamax was to video, warns a report published today. The report, by media and telecoms specialist Enders Analysis, said the launch of the second national commercial digital radio multiplex, headed by Channel 4, might exacerbate the problems rather than solve them, and warned that media regulator Ofcom would face a public outcry if DAB failed. Enders Analysis added that the high cost of DAB transmission and slow growth in revenue had combined to undermine confidence in the new medium and led to the closure of a string of national digital stations. Today's report urged the radio sector to "stop continually beating its chest in public about the wonders of DAB and instead partake in an honest industry debate about the future of the platform".

9 "The exodus of stations from the DAB platform is starting to look like a stampede," said the Enders report, written by Grant Goddard. "With three of the largest radio groups having reduced their commitment to the DAB platform in recent months, their stations having been replaced by a mix of ethnic, religious and noncommercial broadcasters, the future health of the DAB platform must be under question." Goddard's report ends with a chilling prediction from Richard Wheatley, the chief executive of the Local Radio Company, to analysts last month: "DAB is the Betamax of radio." National digital stations that have closed include GCap Media's Core, UBC's Oneword and Virgin Radio's Groove. GCap's Chill and Fun Radio have also been scaled back, while Virgin scrapped plans for a new national digital station, Virgin Radio Viva. The report said the launch of digital stations such as Polish Radio London, Rainbow Radio and BFBS Radio, owned by the British Armed Forces, had worrying echoes of the decline of the AM waveband at the end of the last century. "The DAB platform of 2008, particularly in London, is already starting to resemble the AM platform of 1998, suggesting that DAB might have already been written off by the sector as a means to reach the 'mass market' audiences that national advertisers desire from the medium," it added. Goddard said the launch of the second national commercial digital multiplex, headed by Channel 4, was unhelpful at a time when the first - run by Digital One - was struggling to fill its capacity. "Channel 4 is faced with the task of imminently launching a brand new DAB multiplex in the middle of a snowstorm around the future of the whole platform," his report stated. "By the end of 2007, it was evident that the 'masterplan' for DAB which the radio industry had clung to since the mid-1990s was simply not going to work. "The closure of two longstanding national digital-only stations - Core and Oneword - combined with reductions in the service of several other digital brands helped to crystallise the problems: too much spectrum, not enough consumer hardware takeup, and not enough enthusiasm for DAB from listeners or advertisers." ` Goddard said the issue of DAB overcapacity had to be "urgently resolved" by Ofcom, Digital One, Channel 4 and transmission business Arqiva. He added: "Put bluntly, can the UK commercial radio sector really support two DAB multiplexes? "Ofcom faces a public outcry if the DAB platform were to fail, with owners of the 6.45 million DAB receivers sold to date demanding a refund of their purchases (remember ITV Digital?)." A working group on the future of digital radio set up by the Department for Culture, Media and Sport was due to meet for the first time this week.